1. Field of the Invention
This invention relates to novel aluminosiloxanes, titanosiloxanes, and (poly)stannosiloxanes and methods for preparing these siloxanes.
2. Prior Art
In the prior art, aluminosiloxanes and titanosiloxanes are generally prepared by effecting hydrolysis and condensation reaction of aluminum alkoxides and titanium alkoxides with alkoxysilanes. See Japanese Patent Application Kokai (JP-A) No. 123838/1988, "Inorganic Polymers I," Kajiwara & Murakami Ed., Sangyo Tosho K.K., "Polymer Complex 4, Organometallic Polymers," Polymer Complex Research Association Ed., Gakkai Shuppan Center K.K., and "Outlook on the Application of Inorganic Polymers," Kajiwara Ed., CMC K.K. To form Al--O--Si and Ti--O--Si linkages by these methods, unstable reactants such as condensable silicic acid and silanols and hydrolyzable alkoxysilanes must be used. The hydrolysis and condensation reaction has a drawback that the physical properties, molecular weight distribution, and Si/Al or Si/Ti molar ratio of products vary depending on reaction conditions including the amount of water added, the type and amount of catalyst used, the type of solvent, reaction temperature, and reaction time.
Most aluminosiloxanes and titanosiloxanes obtained by the above-mentioned methods have a wide molecular weight distribution. Depending on reaction conditions, there can be produced components free of an Al--O--Si or Ti--O--Si linkage in a molecule, that is, components whose backbone consists solely of Si--O--Si linkages. Such components are not useful in certain applications.
Further, aluminosiloxanes and titanosiloxanes obtained by the above-mentioned methods are stable only in solvents and when the solvents are removed, undergo gelation to convert into insoluble solids. Without solvents, they cannot be mixed with other ingredients to form compositions.
Stannosiloxanes known in the prior art include stannosiloxanes of formula (10), shown below, which are synthesized by effecting co-hydrolysis of tin chloride with chlorosilanes, reaction of alkyl metal silanolates with tin chloride, and reaction of distannoxane with silanols (see The Chemistry of Organotin Compounds, R. C. Poller, Logos Press Ltd., 1970), and stannosiloxanes of formula (11), shown below, which are synthesized through dealcoholysis reaction between tin alkoxides and silanols (see Y. Abe et al., Bull. Chem. Soc. Jpn., 45, 1258 (1972). To form Sn--O--Si linkages by these methods, unstable reactants such as condensable silanols and hydrolyzable chlorosilanes must be used. EQU R'.sub.3 SiOSnR".sub.3 ( 10)
In formula (10), each of R' and R" is an alkyl or aryl group. ##STR1## In formula (11), R' is a tert-butyl group and R'" is a tri-tert-butoxysilyl group.
It is also known from A. Kasgoz et al., J. Ceramic Soc. Jpn., 100, 763 (1992) that dehydrochlorination reaction between tin chloride and silicic acid yields a stannosiloxane of the following formula (12). ##STR2##
However, this method has a drawback that the physical properties, molecular weight distribution, and Sn/Si molar ratio of products vary depending on reaction conditions including the type of solvent, reaction temperature, and reaction time. Further, polystannosiloxanes obtained by this method remain stable only in solvents and when the solvents are removed, undergo gelation to convert into insoluble solids. Without solvents, they cannot be mixed with other ingredients to form compositions.